|
[Sponsors] |
October 7, 2020, 23:58 |
multiphase interfoam k-omega BC
|
#1 |
New Member
Diego Villegas Díaz
Join Date: Oct 2020
Posts: 4
Rep Power: 6 |
Hi, I am a new foamer. I am simulating a section of an openchanel steady water flow with interFoam solver.
The inlet condition is a water profile and a constant flow in. To represent this situation I used this boundary condition: 1) alpha.water: I used funkySetBoundaryFields to map the waterprofile to alpha.water variable. 1 for water and 0 for air, without intermediate values. 2) U: I used the variableHeightFlowRateInletVelocity with the inlet flow. 3) p_rgh: zero gradient. 4) nut: calulated. 5) k: turbulentIntensityKineticEnergyInlet; with Intensity = 0.0573 6) omega: turbulentMixingLengthFrequencyInlet; with mixing length = 0.00258 I've had some troubles with the k and omega boundary conditions. interFoam fall at the start and I dont understand why. Meanwhile, I am using a fixed value for omega (3.46) or fixed value for k (0.0044065), and its work but I really want to understand why when I use the boundary condition 5) and 6) together interFoam fall. Thaks in advance. |
|
October 8, 2020, 02:08 |
|
#2 |
Senior Member
Charles
Join Date: Aug 2016
Location: Vancouver, Canada
Posts: 151
Rep Power: 10 |
I'm curious how do you get these values, i.e. intensity 0.0573, mixing length 000258, omega 3.46 and k 0.0044065. I guess the divergence was caused by improper initial conditions because turbulence model is prone to diverge.
|
|
October 8, 2020, 09:53 |
|
#3 | |
New Member
Diego Villegas Díaz
Join Date: Oct 2020
Posts: 4
Rep Power: 6 |
Quote:
"Turbulence in open channel flows" (Nezu & Nakagawa) the mixing length scale, k = (3/2)*(I*U)^2, the mixing length for the omega condition I calculated as 0.07*Rh (with Rh the hydraulic radius) I found this scale in these forum but I dont have any formal information. Finally to calculate omega (for fixed value), I calculated another length scale to mixing length lm equal to 0.41*Rh (based in Von Karman constant) and omega is equal to sqrt(k)/lm. I forgot to mention that my system is initialized at the inlet as uniforms values for k, omega and lm, the same values that I mentioned above. May be these unifor initial condition is the reason why interFoam falls. |
||
October 8, 2020, 21:10 |
|
#4 |
Senior Member
Charles
Join Date: Aug 2016
Location: Vancouver, Canada
Posts: 151
Rep Power: 10 |
k = (3/2)*(I*U)^2 is not mixing length, but is turbulent kinetic energy. So, I guess you need to review these initial values.
|
|
October 8, 2020, 23:41 |
|
#5 |
New Member
Diego Villegas Díaz
Join Date: Oct 2020
Posts: 4
Rep Power: 6 |
Ohh I made a mistake writing the last post. I know that k is turbulent Kinect energy. But I'm thinking that interFoam fall due the uniform initial condition un k and omega.
|
|
October 9, 2020, 02:44 |
|
#6 |
Senior Member
Charles
Join Date: Aug 2016
Location: Vancouver, Canada
Posts: 151
Rep Power: 10 |
You have two mixing length. The first mixing length 0.07Rh might be problematic and is too small. You can try 0.41Rh instead.
|
|
Tags |
boundary condition, interfoam, k-omega model, open channel flow |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Multiphase interFoam pipeflow One inlet Two outlets | mwmalkawi | OpenFOAM | 11 | October 1, 2024 08:39 |
Multiphase airwater BC problem in InterFoam | rochamatheus | OpenFOAM Running, Solving & CFD | 1 | March 31, 2019 13:38 |
multiphase explicitsolve function in interFoam | abdo1984 | OpenFOAM Programming & Development | 0 | September 4, 2016 12:26 |
multiphase explicitsolve function in interFoam | abdo1984 | OpenFOAM Running, Solving & CFD | 0 | September 4, 2016 06:45 |
InterFoam wall boundary multiphase | RBJ | OpenFOAM Bugs | 2 | December 3, 2009 06:00 |